The present invention relates generally to microprocessor architecture, and more particularly, to methods and systems for transferring data across different logical voltage domains.
Microprocessors and computers are made from lots of different semiconductor materials. Each type of semiconductor material has a respective voltage level for its logic. For example in some semiconductor or devices a logical one or high state is 5 volts DC. This could be positive or negative 5 volts DC. In a second semiconductor circuit or device using another type of semiconductor technology or structure a logical one or high state could be only 1 volt DC. In yet a third semiconductor circuit or device, using a third type of semiconductor technology or structure, a logical one or high state can be represented by only 0.6 volts DC. In yet a fourth semiconductor circuit or device, using a fourth type of semiconductor technology or structure, a logical one or high state can be represented by only 0.3 volts DC or less.
As a result of these different logical levels used in different types of semiconductor circuits or devices, when transferring a logical one value or high state from, for example the fourth semiconductor circuit (e.g., logical one or high state is represented as 0.3 volts DC) to the first semiconductor circuit (e.g., logical one or high state is represented as 5.0 volts DC), the logical one or high state value must be stepped up or amplified (i.e., shifted) as the logical one or high state value is output from the fourth semiconductor circuit and before being input to the first semiconductor circuit.
Similarly, when outputting a logical one value or high state value from the first semi conductor circuit to the fourth semiconductor circuit, the logical one value must be shifted down to the respective logic levels for the fourth semiconductor circuit.
Typically, this shifting up or down of the logic value occurs in a logic level shifting circuit that is on the same chip as the first semiconductor circuit and the fourth semiconductor circuit. The logic level shifting circuit is typically located between the first semiconductor circuit and the fourth semiconductor circuit. The logic level shifting circuit is in the data path of transferring data from the first semiconductor circuit to the fourth semiconductor circuit and as a result distance and spacing and circuit performance is very important to reduce the time lag or clock cycle count of transferring data from the first semiconductor circuit to the fourth semiconductor circuit. As a result the logic level shifting circuit consumes much valuable area on a chip because it is located between the two semiconductor circuits and not off to one side.
A typical logic level shifting circuit includes two voltage inputs. One input from each of the first and fourth semiconductor circuits. So that the logic level can be stepped up or step down to the respective logic levels corresponding to the semiconductor circuits. However, having two voltage inputs makes the typical logic level shifting circuit more complex than required and therefore consumes more area on the chip. In view of the foregoing, there is a need for a simpler, smaller and faster logic level shifting circuit.